Sensors are used in a number of applications for various reasons. Sensors used in valve system applications, for example, may be designed to determine whether the valve is in an open or closed position (e.g., polarity). Such sensors, and any corresponding circuitry, are typically placed immediately adjacent to the item being sensed. Exemplary sensors used in various applications are disclosed in U.S. Pat. Nos. 4,356,397, 4,931,635, 5,029,967, 5,087,811, 5,343,736, 6,073,650, and 6,118,539.
For example, one conventional valve assembly may include a seal plate assembly, or gate, within a valve duct or fluid passage. The seal plate may be pivotally disposed within the valve duct and may have an outer periphery that conforms with an internal wall of the duct. The seal plate may move or otherwise operate between a first position (e.g., closed) and a second position (e.g., open) within the duct to control the fluid flow. In the first position, the seal plate may be positioned to block the flow path of a gas or liquid by substantially engaging the duct wall in a sealing fashion to close fluid flow in the duct. In the second position, the seal plate is positioned to be less obstructive or generally parallel to the flow path to allow fluid flow in the duct. Exemplary valves, such as for example, a solenoid valve, a butterfly valve, a spool valve, a pilot valve, a bleed valve, a check valve and similar apparatus having one or more flow modulating elements for gas, liquid or other matter, are also shown in U.S. Pat. Nos. 4,428,194, 4,445,532, 4,458,718, 4,768,555, 4,964,422, 4,964,431, 4,967,778, 5,000,213, 5,005,804, 5,029,599, 5,102,097, 5,113,910 and 5,351,934.
Some sensors require electrical circuitry to operate. In some valve assemblies, such sensors may not operate due to certain hostile, harsh or highly volatile environments such as, for example, high temperature environments and/or high vibration environments. These types of environments might exist, for example, in a valve assembly operating on an aircraft turbine engine system or a valve assembly operating in an aircraft environmental control system. In such harsh environments, it is difficult to electronically monitor the position of any moveable component within a valve or other flow modulating element. These types of environments may severely damage a sensor's electrical circuitry due to the high temperature, vibration and/or other harsh characteristics. Moreover, some sensors (such as that shown in U.S. Pat. No. 4,356,397) are designed to provide only complete position polarity information (e.g., valve open or closed, valve on or off; valve high or low; etc.) and fail to provide any indication of the valve's partial or modulated operation (e.g., partially open or closed) and the extent of such partial or modulated operation (e.g., angular or linear displacement).
In view of the foregoing, there is a need for an improved, more robust sensor to detect linear and/or rotational operational characteristics of a valve element (such as, for example a seal plate within a valve assembly) which is operating in various extreme environments, such as a high temperature environment, a high vibration environment and/or like harsh environments. The present invention satisfies this need.